Many weighing systems are known, some dating back to biblical times. More recently, weighing systems have been developed for weighing each one of a stream of articles, such as mail pieces or parcels moving through a transport or mail sorting system. Prior art systems of that type are shown, for example, in U.S. Pat. Nos. 7,096,152 and 3,648,839.
Some known systems rely on back-EMF or “Electro Magnetic Force Restoration” principles. According to one vendor, “an applied load is compensated for by an electromagnetically produced counterforce. A precision position control (optical) keeps the system stable. The slightest movement is detected, initiates a feedback circuit to run current through a coil and causes the load to be returned to its original position. The coil current, which is proportional to the weight, is transmitted to an internal A/D converter then processed in the microprocessor.” See http://www.industrialcontroller.com/wipotec/operation.htm (Wipotec principles of operation).
The need remains for improvements in accuracy, speed (throughput), reduced cost, and reducing the need for frequent re-calibration of weighing systems. The present application achieves these and other goals by applying a dramatically different approach to the problem as further explained below.